Merge changes from TFS

…653496).

[tfs-changeset: 1653598]

Merge changes from TFS

Added github comments to NotImplementedExceptions (that I know about)
and removed a few false-positive NotImplementationException calls.

[tfs-changeset: 1653620]

Merge changes from TFS

Make EventSource.EventMetadata and EventDescriptor public so that analysis roots them.

     These types were public in the separate System.Diagnostics.Tracing assembly, now the move to CoreLib marked them as private.
     While they are technically private (it's a contract used between the library and the ILC toolchain), we need them to be rooted and exported from shared library for the system to work.

     For now I'm simply marking them as public again.
     A cleaner solution might be to use .rd.xml to root them and modify shared library definition to force export them.

[tfs-changeset: 1653635]

--Implement GetRuntimeLookupSignatureNameForClass/GetRuntimeLookupSignatureNameForMethod in bridge code

--GetRuntimeLookupSignatureNameForMethod is used for all usg lookups, regardless of whether method is generic/nongeneric.  In the case of a nongeneric method, I do lookup using TypeDesc instead of MethodDesc.

--Call these from jitinterface instead of the stub code.

--Made method NativeLayoutSignature public so its callable from the bridge

--Made class NativeLayoutSignatureNode public as method NativeLayoutSignature is now public

--Merged method signature and type signature hashtables into a single hashtable GlobalNameLookUpSignatureMap
----This lets us avoid creating multiple SSRs for identical types
----This is a possible perf hit since we're indexing on char* now instead of handles - there are a couple options in the future to mitigate this

[tfs-changeset: 1653636]

Merge changes from TFS

Merge changes from TFS